Catalytic desulfurization of petroleum hydrocarbons



P. MEYER Aug. 5, 1952 CATALYTIC DESULFURIZATION OF PETROLEUM HYDROCARBONS 2 SHEETS-SHEET l Filed April l2, 1949 P. MEYER Aug. 5, 1952 CATALYTIC DESULF'URIZATION OF PETROLEUM HYDROCARBONS 2 SHEETS--SHEET 2 Filed April 12, 1949 ATTORNEYS I Patented Aug. 5, 11952 l CATALYTIG LDESIULFURIZATION OF PETROLEUM HYDROCAR-BONS Percy Meyer, London, England, assignor to Anglo- 'Iranian Oil Company Limited, London, Englandya British joint-stock' corporation l Y Application April 12, 1949,.Serial No.,87,068

I-n Great .Britain April19, 1948 Patent No. 2,574,445, and 68,416, Patent No.

2,574,446, there is described a process'for the hydrocatalytic desulphurization of naphthenecontaining petroleum fractions Which'is carried out by means of hydrogen derived solely from the fractions during the course oi the process. The fractions are passed invaporform over a sulphur-resistant dehydrogenation-hydrogenation catalyst, preferably one comprising the oxides of cobalt and molybdenum deposited on a. support, at a selected temperature within the range approximately 650800`F. and at a selected pressure Within the range vapproximately 25-500V lb./sq. in., whereby .an amount of hydrogen is obtained by dehydrogenation oi naphthenes contained in the fractions not lsubstantially greater than that required toconvert organically combined sulphur in the fractions into hydrogen sulphide andto maintain by hydrogen recycle the pressure in the reaction Azone. vSuch a process may conveniently be referred to as an ,autoning process.

In carrying out such processes, it has .been the practice to recover a desired fraction from the crude oil by conventional methods and. then to'subject the fraction to the autoning process for the reduction of its sulphur content. Such amethod of operation thus involves the preliminary separation of the desired Afraction which has to Vhe re-vaporised:whenrsubjected to the autoningprocess. Itiurthermore,` the autoiining process can only be effectively, carried' out on fractions which contain a sumcient proportion of naphthenes to generate vsufficient hydrogen to maintain the vapour phase. To some extent, the deficiency of naphthenes'inl a speciiic fraction may be remedied by,blending the fraction lWith another fraction .which is richer in naphthenes, but the scope of this expedient is limited by thev characteristics of the available fractions. Yet again, the autoning process can only be effectively applied to fractionsavhich are capable ofbeing recovered from the crude oil Without deleterious effect on their desirable properties. Thus, it is diicult to separate the waxand lubricating'oil. fractions from the crude oill by .distillation Without thermal decomposition or cracking, but it'is, nevertheless,` highly desirable to provide a method of desulphurising such fractions.

. It is among the objects ofthe present inven- 2 tion'v to `provide a :continuous processl for#Y the catalytic desulphurisation of'petroleum fractions derived from crude oil, or of mixtures of-cr`ude oil distillates and residues, in Which the-bolling range of the fractions subjectedfto desulphurisation may be controlled within very wide limits. It is another object of the invention to enable the autoning process to ble-"applied to the selected fraction without the necessity of previously isolating the fraction f'from thecrude-other than in thev course lof theprocess. Yet another object of the invention'isv'tof-enable fractions Which are with difficulty volatilised to be isolated fromcrudeoil-andsubjected to the autoning process ina continuous process under conditionsin-Which there is no "cracking orV thermal decomposition ofthe fractions.'

According to the invention'a process forthe catalytic desulphurisation of petroleum fractions comprises passinga crude oilorya mixture of crude oil distillatesor residues Atira. primary distillation column, passingv the overhead'product from said column to an auton'in'gfzo'ne, passing vthe products from I*the autoiining 'zone to a distillation column for the separation'of the hydrogen and hydrogen sulphide as overhead product, and' the vrecovery of 'one or 4more desulphurised fractions, and passing some Aor all of said hydrogen-containing gaseous'- fraction and, if desiredyany Vor all of'said desulphurised fractions to the base `of the primary distillation column to control the degree of'vapcrisation achieved in said column and thereby-to'control the boiling range'of thejiraction'submitted'to autoining.

According to one-method of -carrying'theflnf vention into effect, the 'crude oil is; 'rst debutanised vin va conventional distillation "column, and the debutanised 4crudevaporised-arid passed to the primary ydistillation vcolumn Vforv the separation overhead of the fraction to VVMbe autoned, the degree of distillation in therprimary column being kcontrolled by the admission of hydrogen to the base of the -column `anti/or by means of reflux returned to the top of the column. If the fraction submitted'to1 Athea-utofning zone is decient in naphthenes, y'such deficiency may l`be made `good *by "recycling naphthene-containing Alight hydrocarbon 'fractions recovered Vfrom -the products iottheautofiningoperation to the crude voil tobe-vaporised or to the base ofthe column vin adxnixturerfwith the hydrogen recycled thereto. If desiredpalso', such light hydrocarbons may be Ireturnedf-to the top of the primary distillation columnas.

reux. i 1 i varied according to the nature of the crude oiland the desired boiling range of the fraction to be autoned.

'I'he asphaltic residue recovered from the deasphalting process may be distilled for the recovery of paraflinic precipitant and the asphalt blended with hydrocarbon fractions recovered from the products of the autofining process for the production of fuel oils. Paraflinic asphaltprecipitant may also be recovered from the products of the autoning reaction and after being separated from the asphalt may be returned to the de-asphalting stage. If desired, some of the paraninic. asphalt-precipitant may be recovered from vthe'liquid vcle-asphalted mixture prior to the entry of the mixture into the autofiningr zone.

According to ak modification of the. last described method of operation the de-asphalted mixture maybe treated, as by cooling, by varying the content ofhydrogen, of paraflinic or of recycle hydrocarbons, or by varying the temperatureand pressure to separate the mixture into a'solid phase, comprising mainly Wax, and a liquid phase, comprising non-crystallisable liq uid fractions. Either the recovered Wax, or the residual liquid, may then be passed to thev autoflning zone.. Two examples of process according to the invention will now be described with reference to Figures 1 and 2 respectively,vof the accompanying drawings.. L Referring to Figure l, crude oil enters at I and passes to a conventional distillation co1- umnv 2 equipped With conventional reux condenser Y3, and means for heating the oil. VIn this column the most volatile fractions of the crude oil, Vsuch as air, methane, ethane and light hydrocarbons generally, are distilled off and withdrawn at 4, 5. The residual oil (now free fromdissolved gases and from such light hydrocarbons as it is desiredor found preferable to remove at this state) is passed into a vaporising furnace 1. Before entering the furnace, hydrogen arisingfrom the process may be injected into the oil at 6; and there may at the same time be injected at this point a recycle stream of light distillate such as will yield sucient' free hydrogen to maintain a more than adequate supply of self-generated hydrogen` Water, if present in the crude oil, may be distilled voff in column 2, but Water or water vapour ifv found advantageous to catalyst performance may be injected at 6 and/or at 9. Leaving the furnace '1, the partially vaporised mixture passes to a fiash vessel 8, from which vapours are separated overhead at I 3, and tar or asphaltic residue is separated at I2. To assist stripping the tar of fractions which are With difculty volatilised, the flash vessel 8 is tted With a perforated pipe II,vv into Which hydrogen, light hydrocarbons, and/or'steam, lmay be passed, these being preheated if necessary, to a suitable temperature by heater -IIJ. Y 'y The vapours leaving the flash vessel 8, are

controlled as to content of high-boiling components by reux returned to the top of the ash vessel, and the total vapours at I3 consist of a mixture of (a) Hydrocarbons freshly produced from the in-put crude oil.

v(b) A carrier such as hydrogen and/or recycle hydrogen-donating hydrocarbons.

Leaving the bottom of vessel 8, as liquid at I2', is a non-vaporised residuum which may range from light fuel oil to asphalt.

From I3, the mixed vapours pass to a furnace I4, in which the temperature vis adjusted to suit the desired performance of the catalyst I5.

lShould the temperature leaving I3 be too high to suit'the catalyst, the furnace I4 would not be operated, but the refiux or quench system at the head of vessel 8, the heaters of 'I and I, and the hydrogen or hydrocarbon recycle rate at 6 and 9 would be adjusted to give the desired temperature. v In passingr over the catalyst, part of the freshly distilled and/or recycle hydrocarbonsr decompose togenerate hydrogen which, togetherl with the recycle hydrogen, converts most of the sulphur present in the oil to hydrogen sulphide.

The drawing illustrates a 'batcliwise operation, the catalyst beingregenerated at intervals, but it is to be understood that a moving-bed or uidised catalytic process could lbe employed.

After leaving the catalyst chambers, the vapour is cooled at I6 and passes to a vapourliquid separator at I1, from which non-condensed gas consisting mainly of hydrogen is recycled via line I8 and compressor I9 tol feed points 6, 9. In the course of operation the process generates excess hydrogen which mayrconveniently be withdrawn for storage or other disposal,' at point 20. rIhe condensed liquid products from I1 are now subjected to conventional distillationat 2|, giving overhead gas which Ymay be treated for purification or vsulphur recovery (2 2, 23), compressed (24) and recycled; and giving also hydrocarbonstreams such as 25,'26, 21 which may as necessary constitute the desired" desulphurised product, or may when requiredfbe recycled via 28 to 6, 9, to donate hydrogen, or may be further fractionated or refined, to give finished products'.

Figure 2 illustrates a' process wherein a liquid-phase precipitation of'non-vola'tile asphaltic components is iirst'elected. The crude oil or topped residuum enters at Iand'is contacted in vessel 2 with asphalt precipitants such as dissolved hydrogen, methane, ethane, propane, butane or similar light hydrocarbons entering at 3. A

From the bottom of vessel 2, asphaltic residues are discarded via stripper 4, for disposal at 5, the light paranic precipitants being distilledoff, and recycled to 3, While the asphalt is blended-With oils arising from I2, 25, 2S, 21, to give -a marketable quality of fuel oil or asphalt. From the top of vvessel 2, the de-asphalted mixture of oil and asphalt-precipitant passes through a heating system, such as a furnace with heat exchangers etc., indicated at 1. Prior to entry to the heating system, hydrogen may be introduced Vinto the light hydrocarbon-oil mixture at 6, to assist vaporisation, or'alterna tively, the de-asphalted mixture of oilV and asphalt precipitant may rst be treated for WaX recovery by conventional methods, and either the oily components of the crude oil; or the waxy solid-phase-components of the crude oil, mixed oil blending, or otherwise removed from the system. Y

The issuing vapours now pass to furnace or heater I4, in which the temperature is adjusted to suit the desired performance of the catalyst I5. Should the temperature leaving I3 Iloe too separating a number of desulphurized fractions from the products of the autofining zone; re-

cycling a proportion of the lighter of said desulphurized fractions to said distillation column; and, recovering the remainder of said desulphurized fractions as desired products.

5. The process of claim 1 in which the feedstock is a debutanized crude oil, including the high to suit the catalyst, the furnace I4 would 'Y not be operated, but the reflux or quench system at the head of vessel 8 and the hydrogen or hydrocarbon recycle rate at 3, B, and 9, would be adjusted to give the desired temperature.

I claim:

1. A continuous process for the hydrocatalytic desulphurization of petroleum hydrocarbons, which comprises the steps of: passing a naphthene-containing feedstock selected from the class consisting of crude oil, and mixtures of crude oildistillates and residues to a primarydistillation column; recovering as an overhead product of said column a vapor mixture of normally gaseous and normally liquid components including a content of hydrogen-donating naphthenes recovered in a later step of the process and recycled to said column; passing said overhead product to an autoning zone wherein said overhead product is contacted with a sulphurresistant hydrogenation-dehydrogenation catalyst at a selected temperature within the range S50-800 F. and at a selected pressure within the range 25-500 lb./sq. in., whereby an amount of hydrogen is produced by dehydrogenation of naphthenes contained in said overhead product not substantially in excess of that required to convert organically combined sulphur contained in said overhead product into hydrogen sulphide and to maintain said pressure in said autofming zone; separating the products from said autoning zone into a gaseous fraction comprising.

hydrogen and hydrogen sulphide, and at least one normally liquid desulphurized fraction; controlling the degree of vaporization achieved in said distillation column and thereby the boiling range of said overhead product and simultaneously correcting any deciency in theY content of hydrogen-generating naphthenes in said feedstock, by recycling a proportion of said gaseous fraction to the base of said distillation column and recycling a proportion of said desulphurized fraction to said distillation column, the proportion of each depending upon the desired boiling range of said overhead product and the naphthene deficiency in said feedstock; and, recovering said desulphurized fraction as a desired product.

2. The process of claim 1 including the step of removing hydrogen sulphide from said gaseous fraction before recycling.

3. The process of claim 1 in which each said proportion is recycled 4. The process of claim 1 including the steps of steps of: separating a number of desulphurized fractions from the products of the autoflning zone; recycling the lighter of said fractions to the top of said primary distillation column as reilux and recycling a proportion of the other desu1.

phurized fractions to the base of said column in admixture with the proportion o f said gaseous fraction being recycled to said base; and recovering the remainder of said desulphurized fractions as desired products.

to the base of said column. Y

` G. The process or claim 4 in which said proportion of said lighter fraction is recycled to the base of said primary distillation column.

7. The process of claim 4 in which said proportion of said lighter fraction is recycled to the top of said primary vdistillation column as reflux.

8. The process of claim 4 in which the feedstock is an asphaltic crude oil, including the steps of de-asphalting the crude oil; and, passing the de-asphalted crude oill to said primary distillation column.

9. The process of claim 4 in which the feedstock is an asphaltic crude oil including the steps of contacting the crude oil with asphalt precipitants selected from thel class consisting of dissolved hydrogen, methane, ethane, propane and butane under a pressure of up to lb./sq. in.

yand a temperature between .0 F. and 200 F., and -then passing the vaporized de-asphalted crude ane, ethane, propane and butane; separatingthe' de-asphalted mixture in to a Wax phase and an oil phase; and, passing one of said phases to said primary distillation column in admixture with the hydrogen and light hydrocarbons being recycled thereto.

11. The process of claim 5 in which said proportion of the other desulphurized fractions is recycled to said column in admixture with the debutanized crude oil supplied thereto.

12. The process of claim 7 in which the'feedstock is crudeV oil, including the steps of :V debutardzing the crude oil; vaporizing the debutanized crude oil; and, passing the vapor to said primary distillation column.

PERCY MEYER.

REFERENCES CITED The following references are of record in h file of this patent: t e

UNITED STATES PATENTS Number 

1. A CONTINUOUS PROCESS FOR THE HYDROCATALYTIC DESULPHURIZATION OF PETROLEUM HYDROCARBONS, WHICH COMPRISES THE STEPS OF: PASSING A NAPHTHENE-CONTAINING FEEDSTOCK SELECTED FROM THE CLASS CONSISTING OF CRUDE OIL, AND MIXTURES OF CRUDE OIL DISTILLATES AND RESIDUES TO A PRIMARYDISTILLATION COLUMN; RECOVERING AS AN OVERHEAD PRODUCT OF SAID COLUMN A VAPOR MIXTURE OF NORMALLY GASEOUS AND NORMALLY LIQUID COMPONENTS INCLUDING A CONTENT OF HYDROGEN-DONATING NAPHTHENES RECOVERED IN A LATER STEP OF THE PROCESS AND RECYCLED TO SAID COLUMN; PASSING SAID OVERHEAD PRODUCT TO AN AUTOFINING ZONE WHEREIN SAID OVERHEAD PRODUCT IS CONTACTED WITH A SULPHURRESISTANT HYDROGENATION-DEHYDROGENATION CATALYST AT A SELECTED TEMPERATURE WITHIN THE RANGE 650-800* F. AND AT A SELECTED PRESSURE WITHIN THE RANGE 25-500 LB./SQ. IN., WHEREBY AN AMOUNT OF HYDROGEN IS PRODUCED BY DEHYDROGENATION OF NAPHTHENES CONTAINED IN SAID OVERHEAD PRODUCT NOT SUBSTANTIALLY IN EXCESS OF THAT REQUIRED TO CONVERT ORGANICALLY COMBINED SULPHUR CONTAINED IN SAID OVERHEAD PRODUCT INTO HYDROGEN SULPHIDE AND TO MAINTAIN SAID PRESSURE IN SAID AUTOFINING ZONE; SEPARATING THE PRODUCTS FROM SAID AUTOFINING ZONE INTO A GASEOUS FRACTION COMPRISING HYDROGEN AND HYDROGEN SULPHIDE, AND AT LEAST ONE NORMALLY LIQUID DESULPHURIZED FRACTION; CONTROLLING THE DEGREE OF VAPORIZATION ACHIEVED IN SAID DISTILLATION COLUMN AND THEREBY THE BOILING RANGE OF SAID OVERHEAD PRODUCT AND SIMULTANEOUSLY CORRECTING ANY DEFICIENCY IN THE CONTENT OF HYDROGEN-GENERATING NAPHTHENES IN SAID FEEDSTOCK, BY RECYCLING A PROPORTION OF SAID GASEOUS FRACTION TO THE BASE OF SAID DISTILLATION COLUMN AND RECYCLING A PROPORTION OF SAID DESULPHURIZED FRATCION TO SAID DISTILLATION COLUMN, THE PROPORTION OF EACH DEPENDING UPON THE DESIRED BOILING RANGE OF SAID OVERHEAD PRODUCT AND THE NAPHTHENE DEFICIENCY IN SAID FEEDSTOCK; AND, RECOVERING SAID DESULPHURIZED FRACTION AS A DESIRED PRODUCT. 